When making diagnoses of the insides of objects, doctors and the like widely use a radiation medical imaging diagnostic apparatus typified by an X-ray computed tomography (X-ray CT) apparatus, an X-ray diagnostic apparatus, a single photon emission tomography (SPECT) apparatus, a positron tomography (PET) apparatus, and the like. Assume that the following description including that of the embodiments will exemplify an X-ray computed tomography apparatus.
Before executing object scanning (actual scanning), that is, irradiating an object with X-rays, an X-ray computed tomography apparatus executes correction (calibration) by using offset data acquired by a DAS (Data Acquisition System) in a state of no irradiation with X-rays.
With the lapse of a predetermined time, however, offset data acquired in advance deviates from offset data included in data obtained by actual scanning (offset drift). This causes artifacts. For this reason, a general X-ray computed tomography apparatus obtains offset data again when a predetermined time elapses, and executes correction by using the offset data obtained again.
When performing scanning accompanied by long-time imaging without allowing to use any quiescent time, such as shuttle helical scanning, it is impossible to properly obtain offset data again, resulting in the difficulty in suppressing artifacts.